PowerPhotos Help
Exporting from iCloud Photos
When exporting photos from a library syncing with iCloud Photos, PowerPhotos will automatically ask Photos to download the full resolution photo if necessary so that it can export based on the highest quality image available. However, do note that if you have the “Optimize Mac Storage” option enabled, then performing an export and forcing a whole bunch of downloads will make your library consume more disk space, potentially filling up the drive if you are exporting a large number of photos. If you want to do an export of your entire library and don’t have enough storage space on your internal drive, then you might consider moving your iCloud library to an external drive first, then performing the export from there.